1. Field of the Invention
The invention relates to roll-up door assemblies. In one of its aspects, the invention relates to blow molded panels for use in roll-up doors. In another of its aspects, the invention relates to molded plastic panels that simulate wood panels and are interchangeable with wood panels in roll-up doors. In still another of its aspects, the invention relates to a roll-up door assembly formed of blow molded plastic panels. In another of its aspects, the invention relates to a method of making a blow molded panel for use in a roll-up door assembly.
2. Description of the Related Art
Trailers for use with semi-tractors and trucks, which can be constructed separately from the semi-tractor or truck and attached thereto or constructed integrally with the semi-tractor or truck, have long used roll-up doors at an inside opening of the trailer to control access to an interior of the trailer. Roll-up doors are often preferred over vertically-hinged, outwardly-swinging doors because the roll-up doors operate within the physical space already occupied by the trailer and do not require space beyond the trailer. The roll-up door is moveable between an opened position and a closed position while being maintained entirely within the interior of the trailer, whereas the swinging doors require room along the sides of the trailer to swing from a closed position to an opened position. If the trailers are to be parked side-by-side, the swinging doors must be opened prior to parking the trailer, or the trailers must be parked far enough apart to permit the doors to swing from the closed position to the opened position, both of which are an inconvenience to the operator.
Roll-up doors typically comprise multiple panels, stacked edgewise one atop the other. The adjacent edges are connected together with hinges to form the entire door so that the panels can pivot with respect to each other. The hinges are normally located on or near the adjacent longitudinal edges of the panels. There are generally two main types of hinged structures that can be categorized by the direction in which the panels must be assembled relative to the longitudinal axis of the panels. One hinge structure requires that the panels be slid laterally (in the same direction as the longitudinal axis) to hingedly couple/uncouple the panels. Another structure requires that the panels be moved to transversely or perpendicular to the longitudinal edge to hingedly couple/uncouple the panels.
Each panel usually includes a roller assembly near each of the opposite latitudinal edges. Each roller assembly comprises an axle that rotatably supports a roller or wheel. The axle is mounted to the panel directly or, alternatively, through a hinge positioned adjacent or near the latitudinal edge. The roller is received within a track mounted within the interior of the trailer near the inside opening. As the door is raised from the closed position to the opened position, the rollers travel along the track to move the panels from a vertical position closing the inside opening of the trailer through a 90° curved section to a horizontal position overlying the interior of the trailer and exposing the inside opening of the trailer. The panels rotate relative to each other as needed about their respective hinges. The panels are constrained in their movement by the receipt of the rollers within the track. Thus, the maximum angle of rotation between any two panels can be controlled by the arc of the track.
Roll-up doors have several known problems or disadvantages. Many roll-up doors have panels that are made entirely of solid material, such as wood. The resulting door is exceptionally heavy and requires counter-balancing springs to lift and close the door. The counter-balancing springs reduce the usable volume of the trailer, which is highly undesirable given the great value placed upon usable volume for a trailer. In addition, the panels as well as the counterbalancing spring add to the trailer undesirable weight which adversely affects fuel efficiency and thus profits.
Attempts to address this problem have focused on using lighter weight materials, especially extruded plastics. The resulting extruded panels are relative light in weight, but they often require special or complex hinge systems and special structural stiffening to accommodate the mounting of the roll-up door hardware such as handles and latch assemblies.
Many roll-up doors are often time-consuming to repair. When a roll-up door is damaged, usually the repair is accomplished by merely replacing one of the multiple panels. Unfortunately, some plastic roll-up doors have a panel and hinge configuration that requires the removal of multiple or all of the panels to replace the damaged panel. Panels that have hinges that require the lateral sliding of the panels for assembly further exacerbate the replacement of a single panel in that all of the panels preceding the damaged panel must be removed from the tracks before the damaged panel can be laterally slid and uncoupled from the adjacent panels. However, current wood panel doors do not require a complete disassembly of all panels and can usually be repaired by removing the damaged panel and replacing it with a new wood panel but not with a plastic panel.
U.S. Pat. No. 3,980,123 to Vago discloses using blow molded panels formed of polyethylene in garage doors and the like. The panels are mounted in a rigid framework that include horizontal rails spanning the length of the door and connected vertical stile supports which span the height of the door. The horizontal rails protect the top and bottom sides of the panels and the vertical stile supports are hinged together to form the door. The hinges on the sides of the door include rollers movably mountable in tracks of an aluminum door frame. The panels include ribbed configurations on an inside wall for strengthening purposes. Dead air spaces are formed as cavities during blow-molding through the shaping of an outside wall with respect to the inside wall.
U.S. Pat. No. 6,826,887 to Skov discloses a blow-molded panel for use in a variety of applications, namely in forming storage units. The panel includes lateral slots for enhancing the structural integrity of the panel. The panel also includes a plurality of transverse ribs extending through the lateral slots for additional strengthening.
U.S. Pat. No. 4,762,379 to Beam et al. discloses blow-molding a panel comprising a plurality of depressions in a rear wall that extend to a front wall and that are fused thereto for structural rigidity. The panel is formed by blow molding in a mold cavity formed by the engagement of a first mold plate and a second mold plate. Multiple projections on the second mold plate are used to form the depressions during the molding process. Due to the restriction of the mold cavity by the projections, a plurality of blow needles project through the second mold plate such that air can be blown into each section created by the projections.
U.S. Pat. No. 7,210,277 to Steed discloses blow molding panels for use in a partition system for outdoor structures such as fences and sheds. The panels include edges with steel reinforcements. The partitions also have patterns on both sides formed by rows and columns of depressions that extend towards or engage an opposing surface. The patterns on both sides of the partitions include one or more depressions and the depressions are generally aligned so that a depression on one side of a panel is aligned with a depression on the other side of the panel. In addition, the patterns on the panels include grooves, and the depressions are formed at the intersection of the grooves. The depressions are integrally formed in the panels are said to be configured to increase the strength of the panels. Because the depressions are formed on both sides of the panel, the opposing sides of the panel may have generally the same pattern.
United States Patent Application Publication No. 2007/0209295 to Mower et al. discloses a shed comprising blow-molded panel walls. The walls can include reinforcements to provide greater strength, rigidity, impact resistance, resilience and/or ability to prevent deformation. In order to reinforce the panels, the reinforcements can have different capabilities or characteristics than the panels, such as different strength, resilience, compression and/or tension capabilities that the panels, and the reinforcements may be arranged or configured to maximize the strengths or characteristics of the thereof.
U.S. Pat. No. 6,955,206 to Mullet et al. discloses a sectional door comprising a plurality of panels formed by extrusion. The door can contain reinforcing members in form of tubes, which can be inserted into the panels after the panels are extruded and extended across the entire width of the panels. In addition, the tubes are exposed at both ends and form journals for axles of wheels. U.S. Pat. No. 6,672,362 is in the same family as '206 to Mullet et al. and discloses a similar panel construction.